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  1. #1
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    WiMAX: RSSI and CINR relation to modulation

    Hi all,

    actually i want to ask about which parameter better to use changing modulation of WiMAX on radio link, RSSI or CINR?, as i know RSSI and CINR maybe can change in different way, if RSSI degradate much, maybe CINR not (vice-versa).

    We can calculate RSSI from equation in standard 802.16e (8.4.13.1.1), but how to calculate CINR (not only CNR or SNR)?

    from standard there's only receiving SNR threshold for WiMAX modulation and coding rate, how about the interference?, is that same if i assume that the interference same in noise if i measure the real condition in air interface? (i mean if i have the same CINR threshold like SNR threshold?

    Thanks for anyone if want to discuss

    •   Alt18th November 2009, 10:20

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    Re: WiMAX: RSSI and CINR relation to modulation

    I am not an expert in this kind of physical layer stuff, but from my understanding the decision to change the modulation (Adaptive Modulation) is based on SNR, and Power Control is based on RSSI reporting.



    •   Alt18th November 2009, 21:06

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  3. #3
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    Re: WiMAX: RSSI and CINR relation to modulation

    if i have good SNR but i have bad interference, how can i have a good modulation and coding rate?, in real wimax band frequency in air interface we have really bad interferences, actually i want to ask also, in noise floor:

    Noise floor = -174 + 10 Log Bw (Hz) + N.Figure

    this noise not include interference right?, are any of you have experience in measure real interference in air interface for WiMAX band frequency or others wireless system

    Thanks



    •   Alt19th November 2009, 02:04

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  4. #4
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    Re: WiMAX: RSSI and CINR relation to modulation

    Yes, but in the same time the RSSI is affected also by strong interferences as, Adjacent Channel, Inband Blocking, Cochannel Interferer, etc.
    So, probably the best channel estimation is to do a combination of both, BER and RSSI, where BER is proportional with SNR.

    In your Noise Floor formula you forgot to add the gain.

    Noise Floor[dBm] = – 174 + 10*LOG BW[Hz] + Noise Figure[dB] + Gain[dB]

    Strong interferer could saturate the front-end, and raising in this way the overall noise floor.



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    Re: WiMAX: RSSI and CINR relation to modulation

    Ok, thanks for helping me, i think i have understood



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    Re: WiMAX: RSSI and CINR relation to modulation

    In your Noise Floor formula you forgot to add the gain.

    Noise Floor[dBm] = – 174 + 10*LOG BW[Hz] + Noise Figure[dB] + Gain[dB]
    actually you do not need to add the gain. The gain of the front end effects both the signal and the noise. So when you calculate the SNR it will be canceled off.



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